Why 0.00000001 Resolution?

My understanding is the best CNC machines are accurate out to five decimal places. I saw some numbers like 0.00007. When we use to cut lobe models on manual milling machines we were able to go out to five decimal places using a dial indicator. The fifth decimal place was a "precise estimate" from the operator.

You might wonder why do cam profile lift tables go out to eight decimal places since the best machines are only good to five decimal places? The eight decimal places are necessary to create a smooth velocity, acceleration, and jerk curve for the cam profile. With five decimal places the curves are very jagged and hard to analyze. The lift curve is really the only curve that will work with five decimal places but to properly design a cam profile, smooth velocity, acceleration, and jerk curves are necessary.

Since the cam profile is designed to eight decimal places and only machined to five decimal places the finished lobe profile is not exactly the same as the design, close but not exactly the same. The old manually made lobe models were even farther away from the design but still worked just fine.

I use this saying all the time: "There are three cam profiles, (1) the original design, (2) the finished lobe, and (3) the cam profile in a running engine." All three are different. Don't get caught-up in worrying about numbers being exact.